Description

Io, Ganymede and Callisto won the ``clean up the office'' event
at the annual Mobile Robot Competition sponsored
by the American Association for Artificial Intelligence (AAAI).
The small robots, which look like miniature tanks, were programmed
to clean up an office littered with soda cans, coffee cups and wads
of paper. The group from Georgia Tech won the
event by collecting more trash
in ten minutes than any other team's robot.

Each year, teams of researchers and students from industry and
academia bring their robots to the AAAI competition, which challenges
them with a "real world" task. This year, the organizers offered two
tasks; contestants could try either one or both. The first task
involved navigating an office using an electronic map. The other was to
clean up an office littered with soda cans, coffee cups, and crumpled
paper. The contest was held in Seattle with teams from Stanford,
Carnegie Mellon University (CMU), Lockheed Missiles and Space, the
University of Chicago, the Colorado School of Mines, Simon Fraser
University, the University of Bonn (Germany), Georgia Tech and others.

Georgia Tech's robots are programmed with a "reactive" system
called motor schema-based control. Motor schemas can be thought
of as low-level behaviors; "avoid obstacle" and "move to the
goal" are examples. More complex behaviors are constructed by
"adding" several motor schemas together. The robots sequence
from one behavior to another as they accomplish their task of
gathering trash.

Initially, a tiny color camera guides the robots to trash, which they
grab with a specially-designed gripper. The robot's vision is sometimes
fooled, so they may grab non-trash objects like table legs.
But they can tell the difference since tables don't move when
small robots try to carry them away; objects that do move are
considered trash. Once a robot has a piece of trash in hand,
it searches for a trash can, again using vision. After locating a
trash can and moving to it, the robot drops the trash nearby.

Many people wonder why the robots are painted fluorescent green.
Although it does make them a bit more flashy, there's another reason.
Bright green is easy for the robots to see, so they use it to keep
tabs on one another. They "cooperate" by moving away from each other,
preventing interference and allowing them to cover a large area
faster.

Even though the robots performed well, there was one problem:
the competition trash cans were black, so the robots were programmed to
move toward the darkest objects to deliver trash. Unfortunately, they
confused dark shadows under tables with trash cans. The result was
that they sometimes hid trash under furniture instead of throwing it
away. Maybe that's just a sign that robots are becoming more human
all the time.

The Georgia Tech team is a multi-disciplinary group of students and
engineers led by Tucker Balch and advised by Professor Ron Arkin.
Team members included, from the College of Computing: Tucker Balch,
Gary Boone, Harold Forbes, Ray Hsu, Doug MacKenzie, and Juan Carlos
Santamaria; from the School of Mechanical Engineering: Erik Blasch;
from GTRI: Tom Collins and Dave Huggins; and Claudia Martinez, a visiting
student from Mexico.